To study the molecular biology of eye development, I am isolating cDNA clones for high molecular weight lens proteins. Type IV collagen is a major constituent of the lens capsule. Its subunits are coded for by a large messenger RNA of at least 5000 nucleotides. I have constructed a cDNA library in the plasmid pBR322 using high molecular weight RNA (greater than 4500 nucleotides in length) from total chick embryos. This library is screened with in vitro labeled high molecular weight RNA from embryonal chick lenses. Thirty-five cDNA clones from a total of 4200 clones hybridized specifically with the labeled lens RNA. By counter selection with RNA's from different tissues that contain different types of collagen (RNA from cartilage and RNA from chorionallantois membranes), two prospective type IV collagen specific cDNA clones were selected. These clones are being further analyzed.